1. Field of Invention
The present invention is a pipe joint gasket forming a seal between two cooperating pipes or vessels where one is inserted into the other.
2. Prior Art
Pipe gaskets of similar nature to the present invention are known in the water pipe industry. Pipes of varying materials share a common need to form a seal between two cooperating pipes.
It is known that gaskets with retaining rings have been used to seal cooperating pipes as disclosed in German Patent No. 1,118,551 to Halbach et al., British Patent No. 1,033,756 to Carter and U.S. Pat. No. 4,379,559 to Bohman.
U.S. Pat. No. 2,963,398 and German Patent No. 85/04462 to Nowack teach a gasket device that uses a dual hardness gasket instead of the retaining ring. The advantage of the dual hardness feature is that the gasket is more secure in the outer pipe prior to and during insertion of the inner pipe.
The gaskets disclosed by prior art all have either internal or external contour or both that do not match the surfaces of the pipes that they must seal. For example, Nowack teaches an air gap formed between the exterior contour of the gasket and the inside surface of the outer pipe after the joint is assembled. Others teach similar spaces and gaps, some of which close up during the insertion of the two cooperating pipes. The idea is apparently to make use of a point-load contact area to affect a good seal in a relatively small area at the sacrifice of other areas not establishing effective seals. However, this concept only works in controlled conditions. In practical application, uncontrolled and unfavorable pipe laying conditions are often unavoidable. Muddy trenches and under water installations, for instance, produce opportunities for the entrapment of foreign objects or materials between gasket and the outer pipe prior to the insertion of the inner pipe, and adversely affect the integrity of the seal.
The devices described above present many unrelated problems and various drawbacks. Thus a great need exists for an improved gasket to seal two cooperating pipes or vessels.